The present invention relates to a recording or reproduction system for recording or reproducing information by using a recording medium, and in particular to a recording or reproducing system for recording digital signals with a high density.
As an example of a recording/reproducing system for recording/reproducing information, an optical disk system for recording/reproducing image information can be mentioned. As an example of image information, television signals can be mentioned. By the way, television signals commonly watched at the present time are analog signals of the NTSC system. They are handled in the form of analog signal except special cases such as business use. As a medium for recording/reproducing NTSC images, a video tape recorder (VTR) using magnetic tape or a laser disk (LD) using an optical disk is employed. Typically in these cases, analog image signals are recorded on a medium by using the frequency modulation method and mass production is performed by means of transfer.
On the other hand, as the speed of computers is increased, there have appeared such system that images are converted into digital signals and the digital signals are recorded on a medium. These images may be created on a computer or may be taken into a computer individually. In some cases, NTSC images taken in may be converted and taken in. Also the output may be sent to only a computer display. Alternatively, the output may be converted into NTSC signals so that it may be watched on an ordinary television screen. In general, the image information is recorded on a hard disk or a writable optical disk as digital data.
Furthermore, signals of high definition television (HDTV) attracting attention as future television are often recorded and reproduced in the form of digital data because they are often used for business use at the present time. On the other hand, MUSE signals created for domestic use of high definition television are analog signals and broadcasting is performed by using MUSE signals. Furthermore, optical disks having MUSE signals recorded thereon are manufactured as products. Such a technique has been announced in "Journal of the Institute of Television Engineers of Japan, Vol. 44, No. 10, pp. 1376-1382" as "Signal transmission characteristics of high definition video disk."